1. Field of the Invention
The present invention relates to a stacking-type, multi-flow, heat exchangers, each heat exchanger comprising a plurality of heat transfer tubes, each tube having an inner fin therein and outer fins which are stacked alternately between the tubes, and methods for manufacturing such heat exchangers. Specifically, the present invention relates to a process for manufacturing the heat transfer tubes, each tube having an inner fin therein, and a stacking-type, multi-flow, heat exchanger manufactured by using the methods, suitable as a heat exchanger for use in an air conditioning system, in particular, for vehicles.
2. Description of Related Art
Stacking-type, multi-flow, heat exchangers having alternately stacked heat transfer tubes, each tube having an inner fin therein and outer fins therebetween, are known, for example, as depicted in FIGS. 10–12. In a heat exchanger, thus constructed, a heat transfer tube is formed as in a known heat exchanger, as depicted in FIGS. 10 and 11. Namely, a pair of tube plates 101, each formed as depicted in FIG. 10, are disposed so as to compare each other, as depicted in FIG. 11, and the circumferential edges thereof are connected to each other to form fluid passages 102 therein. An inner fin 103 is inserted into each fluid passage 102 in order to increase the efficiency of heat exchange. Flanges 104 are formed on tube plates 101 at the end portions of each tube plate 101 in its width direction. Flanges 104 are disposed at the front and rear positions in the direction of air flow 40, as depicted in FIG. 12, which is viewed along Line A—A of FIG. 8. Thus, a known heat transfer tube 105 is constructed, for example, as disclosed in Japanese Patent Application No. JP-A-2002-267383.
Such a known heat transfer tube 105 is manufactured, for example, as depicted in FIG. 13. The manufacturing method shown in FIG. 13 has the following steps:
Step 11 (S11): Tube plates 101 and 101′ and inner fins 103 are made as complete parts, separately, and plates 101 and fin 103 are provided in a tube assembling process.
Step 12 (S12): Inner fins 103 are grasped by insertion arm 106 and conveyed toward tube plates 101 and 101′.
Step 13 (S13): Inner fins 103, conveyed by insertion arm 106, are disposed on a first or lower-side tube plate 101 within predetermined cavities so as not to be shifted from the predetermined positions.
Step 14 (S14): Insertion arm 106 is returned to its initial position.
Step 15 (S15): After insertion arm 106 is withdrawn from between tube plates 101, a second or upper-side tube plate 101′ disposed onto the lower-side tube plate 101.
Step 16 (S16): The pair of tube plates 101 and 101′ are secured temporarily to each other, so that the configuration of the heat transfer tube formed by the pair of tube plates 101 and 101′ is not disturbed during the stacking of a plurality of heat transfer tubes and a plurality of outer fins alternately, for example, temporarily secured by caulking to each other by crimping.
In such a method for manufacturing a heat transfer tube, however, at least the following problems remain:
(1) As the number of heat transfer tubes used per heat exchanger increases, the time for assemble increases, and the productivity declines.
(2) It is difficult to accurately position inner fins within the predetermined cavities of the fluid passage forming portions of a tube plate during of the above-described S13.
(3) A positional shift of an inner fin may occur during the covering of first-tube plate 101 with second tube plate 101′ at above-described S15.